Prevention of foaming in steam generation



Patented Mar. 11, 1952 PREVENTION OF FOAMING IN STEAM GENERATION Paul G. Bird and Arthur L. Jacoby, Western Springs, 111., assignors to National Aluminate Corporation, Chicago, 111., a corporation of Delaware No Drawing. Application December 21, 1946, Serial No. 717,824

9 Claims.

It is well known in the operation of steam boilers, such as in electric power plants, railroad locomotives and the like, or in evaporators, that the water therein, even though initially it shOWS very little tendency to foam, will, when the amount of total solids therein approaches a relatively high concentration, develop a very decided tendency to foam. When this occurs, considerable quantities of water are physically carried out of the boilers or evaporators with the steam, thus appearing in the steam lines and in the eventual condensate. Such priming has many disadvantages because it tends to contaminate the steam lines, to plug or corrode the valves, and under serious conditions may even impair the cylinders and piston rods of the steam engines, or the impeller blades of turbines in which the steam is used for the generation of power.

Attempts have been made in the past to control this foaming, by excessive blowdown of the boilers or by the injection thereinto of such materials as castor oil, tallow, and the like. While these fatty materials have some small degree of efficiency, they are, on the other hand, quite deficient in that they introduce new difliculties which, in some instances, are worse than the conditions they are intended to cure. In the first place, these fatty acids or glycerides are unstable under the conditions existing in the boilers, particularly as the pressure and temperature increase, the high temperatures leading to rapid decomposition of the glycerides, which, if anything, will tend to increase the foamingand priming difiiculties. Furthermore, in many instances certain-of the decomposition products thus produced, or sometimes even the materials themselves, have a definite volatility with steam and will, therefore, steam-distil out of the boilers, thus appearing in the steam and in the condensate. This, of course, is also very undesirable. Furthermore, such types of antifoaming agents usually have to be, employed in relatively large quantities, adding. not only to theexpense but also to the inconvenience of operating the steam generators; and thosewhich have a tendency to decompose do so quite rapidly, and hence their effectiveness is of short dura tion, which therefore necessitates the continual charging into the boilers or other steam generators of relatively large amounts of these older antifoaming agents. Moreover, such antifoaming agents are diflicult to use because the amounts in which they are efiicacious are very critical, and any overdosage usually aggravates the diificulty instead of curing it.

One of the objects of the present invention is the preparation of a liquid suitable for the generation of steam in steam generators and comprising water containing dispersed therein a very small amount of a specific type of compound whereby, when such water is heated to the boiling point in a steam boiler or other generator, being thereby evaporated, the concentration of solids therein will not bring about excessive foaming and the resulting priming, the added compound being substantially non-volatile with the steam and stable, so that it will be retained by the water and neither it nor its decomposition products will appear in the steam and the resulting condensation thereof. Other objects will appear hereinafter.

In accordance with this invention it has been found that compounds having the following general formula are of a high order of efiiciency when used as antifoaming and antipriming agents in steam generators operating under superatmospheric pressures:

amines and should contain at least about 14 carbons in the aliphatic acyl radical regardless of the size of the other acyl radical. The aroyl radical may be derived from benzoic acid, substituted benzoic acid, naphthoic acid, substituted naphthoic acid, and their homologs and benzologs. Where an arylsulfonyl radical is employed, it may be derived from the arylsulfonic acids corresponding to the above named aromatic carboxylic acids.

3 The aliphatic acyl radical x-cll is preferably derived from a fatty acid, typical fatty acyl groups being myristyl, palmityl, stearyl, oleyl, ricinoleyl, erucyl and other long chain acyl groups of fatty acids found in animal, fish and vegetable oils.

The aromatic acyl groups which may be linked to any of the aforementioned aliphatic acyl groups through a polyamine include, for example, benzoyl, m-bromobenzoyl, o-chlorobenzoyl, o-iodobenzoyl, p-nitrobenzoyl, p-anisoyl, pbromobenzene sulfonyl, beta naphthcyl, beta naphthalene sulfonyl, p-toluene sulfonyl, cinnamyl, and phenylacetyl.

Examples of the polyamines which may be used in linking together said aliphatic 'acyl and aromatic acyl groups are the monoalkylene diamines having from 2 to carbon atoms (ethylene diamine and its homologs up to and including decamethylene diamine) and the polyethylene polyamines, including diethylene triamine, triethylene tetramine, tetraethylene pentamine and the corresponding polypropylene polyamines. We shall describe hereinb'elow the preparation of several of the materials, and while the examples disclose a few of many satisfactory preparative procedures, in most cases the same product may be obtained by more than one route.

The most-used method of preparation involved the use of the acid and the amine, in nearly theoretical amounts for the product desired, and consisted essentially in the initial formation of the amine salt of the acid, followed by dehydration to the monoamide by heating. The second acid was then introduced and the process continued to give the desired diamide. In certain cases, the use of the acid halide was resorted to in order to introduce an acyl group. In still another very useful procedure, the fatty acid ester was used instead of the acid itself. Thus, while any usual ester can be used, such as methyl, ethyl, glycol, e'tc., the .glycerides of the high molecular weight acids are often very readily obtainable and were the subject of much of the preparative work. By heating the glyceride and the polyamine together in the proper proportions, the alkaline amine causes the ester to be split, liberating the fatty acid, which then reacts with the amine to give the amide. Usually, when using the triglycerides, such proportions were used that two of the three acid chains would be split off from the ester and used, and the re- .maining fatty acid monoglyceride remained in the product as a harmless by-product. However, excellent materials have also been formed where the proportion of triglyceride or other ester used was such that all the availableacyl chains were used in forming the amide. Indeed, the reaction of theoretical amounts of a polyethylene polyamine and a glycerol monoester has yielded useful products.

The number of different compounds which can be prepared is quite numerous, and while we are givin a large number of examples, we do not wish to be limited to those specifically described nor to the species claimed. These examples are as follows:

grams of triethylene tetramine was stirred with heating at 150 degrees C. to 160 degrees C. for 2 ly and heating continued '15 minutes.

4 hours. Then 3.6 grams of commercial stearic acid was added and the process continued another 2 hours. When cool, the product was a brown wax.

Example H A mixture of 6.8 grams of phenylacetic acid and 7.3 grams of triethylene tetramine washeated with stirring at 150 degrees C. to 160 degrees C. for 2 hours. Then 13.5 grams of commercial stearic acid was added and the process continued another 2 hours.

Example III Example IV A mixture of 7.3 grams of triethylene tetramine and 13.5 grams of commercial stearic acid was stirred for '2 hours at 150 degrees C. to 160 degrees C., after which 12.8 grams of p-bromobenzene sulfonyl chloride was added rather rapid- 7 When cool, the product was a hard, brown wax.

Example V A mixture of 13.5 grams of stearic acid and 7.3 grams of triethylene tetramine was stirred for 2 hours at 150 degrees C. to 160 degrees C. Then 9.5 grams of p-toluene sulfonyl chloride was added and the heating and stirring continued an hour. When cool, the product was a clear, brown, resinous solid.

Ezcample VI To 15.6 grams of stearyl triethylene tetramine was added an equimolar quantity of m-bromobenzoyl bromide at degrees C. After '15 to 20 minutes of mixing at 130 degrees C. to degrees C. the reaction was considered complete. When cool, the product was a very hard, tan wax.

Example VII To 23.4 :grams of stearyl triethylene tetramine was added an equimolar quantity of o-chlorobenzoyl chloride, in the same manner as described in Example VII. When cool, "the "product was a hard, tan Wax.

Example VIII To 15.4 grams of stearyl triethylene tetramine was added an equimolar quantity of o-iodobenzoyl chloride in the same manner as described in Example VI. When cool, the product was a glassy, tan "wax.

.Ezcample IX To 21:4 grams of stearyl triethylene tetramine was added an 'equimolar quantity of betanaphthoyl chloride, in the same manner as described in 'Example V'I. When cool, the product was a hard, yellow wax.

Example X To 20.5 grams of stearyl triethylene tetramine was added an 'equimolar quantity of p-n'itrobenzoyl chloride, in the same manner as described in Example VI. When cool, the product was a hard. tan wax. I

Example XI To 20.5 grams of stearyl triethylene tetramine was added an equimolar quantity of p-anisoyl chloride, in the same manner as described in Example VI. When cool, the product was a hard yellow. wax..=

Example XIII To 18 grams of stearyl triethylene tetramine was added an equimolar quantity of beta-naphthalene sulfonyl chloride, in the same manner as described in Example VI. When cool, the product was a glassy, yellow wax.

The products hereinabove described, while not ordinarily considered as soluble in water to any great extent, may be suitably dispersed in water or emulsified therewith, so thatefiective amounts thereof may be introduced and be present in the water within the steam generator under operating conditions. The emulsifying or dispersing agent used must, however, be of a kind that does not cause foaming, either by itself or by its decomposition products. The compounds may be used conjointly with each other 'as well as with other known antifoaming agents, such as, for example, castor oil.

The amounts of these high molecular weight diacyl derivatives of 'polyamines which are required are extremely small, and in general one grain per gallonis ample. however, amounts of as little as ,4 grain per gallon in the feed waterwill still give valuable results, and the amounts may be even further reduced. For example, ,4 grain per gallon of this type of condensation product will suppress foam in a boiler for from to minutes. Comparing this with the efiicacy of castor oil used on the order of 6. grain per'gallon, which will suppress the foam for only about seconds to one minute, it is obviousthat if one'were to use castor oil it would have to be continuously fed into the boiler, with the unavoidable accumulation in the boiler of a lot of soap produced by the reaction of the liberated fatty acids with the alkali present in the water, which would only aggravate the problem.

The diacyl derivatives under discussion, however,

products.

Depending,iof course, upon the degree of concentration of solids, the dosage may be varied, but'one grain per gallonis about as much as would ever have 'to be used even under serious are quite stable and do not yield undesirable bybonditions, and for many purposes ,5 1 grain per gallon and even less can'be used. The process is particularly effective at pressures of about 250 pounds per square inch.

The introduction of the antifoaming compounds of the present invention into the boiler may be accomplished in a number of ways. Thus, the antifoaming compositions may be dispersed or physically mixed with, say, sodium carbonate or some other material used for treating the boiler water and pumped with the feed water into the boiler by means of either an injector or a feed water pump. The compounds may also be dissolved in suitable organic water-miscible solvents such as alcohols, ethers, ketones, etc., and introduced in small measured amounts into the feed water entering the boiler. Suitable mechanical measuring devices which will periodically or continuously inject the required dosage of the antifoaming compounds into the feed water may be used, so that the introduction will be more or less in proportion to the steam consumption to which the steam generator is subjected. Another For many purposes,

6 manner of introducing the antifoaming compounds is to form an emulsion thereof in water and then feed said emulsion either directly into the boiler or the feed water lines leading to it! 'The preferred active antifoam ingredients are oily to waxy substantially water insoluble sub stances characterized by stability in hot aqueous alkaline liquids such as are used in locomotive boilers and under the conditions which are-present in locomotive boilers. Compositions prepared in accordance with the invention have been demonstrated to be particularly effective in locomotive boilers under superatmospheric pressure conditions within the range of 150 to 300 pounds per square inch and the corresponding temperature conditions. Tests have demonstrated that these compositions are effective even at the much higher pressure and temperature conditions in stationary boilers for power plant operations, as, for example, superatmospheric pressures up to 1000 to 1500 pounds per square inch.

Apart from the fact that the preferred active antifoam ingredients function under severe conditions where other so-called antifoam materials are ineffective, the reason for the functioning of these materials is not known. It has been proven in tests connected with the practice of this invention that these materials are very stablelto hydrolysis as compared with many other differ ent types of compounds.

The amounts of an antifoam agent-employed in inhibiting foam will depend upon several factors, among them the conditions under which the foam occurs, the amount of foam suppression desired, the percent of solids in the foaming liquid, the alkalinity, temperature, and pressure of the foaming liquid, the type and degree of agitation, and the kind of gas present in the gas phase of the foam. It is, therefore, impos sible to state any rigid rules for estimating the amount of an antifoam which needs to be used. In general, the antifoam will be added in relatively small amounts, gradually increasing in size, until the foam is controlled to the extent desired. v.

In the prevention of priming in a power plant or locomotive boiler operating at ordinary pres sures, e. g., 250 pounds, it has been found that the effective antifoam compositions of this invention, i. e., those possessing the requisite molecular size for this use, as explained above, are efficient when they are introduced into the feed water at a concentration of the order of magnitude of 0.01 grain per gallon, based on the weight of active antifoam ingredient. Thus, a boiler operating at 10 concentrations, which is not unusual, would have 0.1 grain of active antifoam per gallon of boiler water. Some foam suppression has been obtained with only 6 parts by weight of the active ingredient per billion of water in the feed water going to a boiler. Quantities of from to 500 parts by weight of the active ingredient per billion of water are frequently sufficient merely to improve steam quality. Such proportions have allowed some users to operate with increased dissolved solids of as much as 15% over the amount permissible without the steam conditioner.

Having thus described the invention, what we claim as new and desire to secure by Letters Patent of the United States is:

1. A method of generating steam which comprises boiling, under superatmospheric pressure conditions, water containing an amount of total dissolved solids tending to produce foaming and priming and a quantity of a wax-dike diacylated polyamine in which the polyamine is a polyethylene polyamine, the aliphaticv acyl radical is derived from a fatty acid and contains a carbon chain of at least 14 carbon atoms and the aromatic acyl radical is an aryl sulfonyl radical from the group consisting of aryl sulfonyl radicals of the benzene and naphthalene series, said quantity being sufiicient to substantially inhibit said foaming and priming. v

2. A method of generating steam which comprises boiling, under superatmospheric pressure conditions, water containing an amount of total dissolved solids tending to produce foaming and priming and a quantity of a wax-like diacylated polyamine in which the polyamine is a polyethylene polyamine, one of the acyl groups is an aliphatic acyl group derived from a fatty acid containing at least 14 carbon atoms and the other is an aromatic-aliphatic acyl radical in which the aromatic group is from the benzene series and the aliphatic group contains not more than 3 carbon atoms, said quantity being sufficient to substantially inhibit said foaming and priming.

3. A method of generating steam which comprises boiling, under superatmospheric pressure conditions, water containing an amount of total dissolved solids tending to produce foaming and priming and a quantity of stearyl-phenylacetyl triethylene tetramine, said quantity being'sufiicient to substantially inhibit said foaming and priming. I

4: A method of generating steam which comprises boiling, under superatmospheric pressure conditions, water containing an amount of total dissolved solids tending to produce foaming and priming and a quantity of stearyl-benzoyl triethylene tetramine, said quantity being sufficient to substantially inhibit said foaming and prim- 5. A method of generating steam which comprises boiling, under superatmospheric pressure conditions, Water containing an amount of total dissolved solids tending to produce foaming and priming and a quantity of stearyl-p-toluene sulfonyl triethylene tetramine, said quantity being sufficient to substantially inhibit said foaming and. priming. Y

6. A method of generating steam from a boiler water havng a tendency to foam on boiling which comprises dispersing into said water a wax-like diacylated polyamine in which one of the acyl groups is derived from a. fatty acid containing at least 14 carbon atoms.v the other acyl group is derived from an aromatic carboxylic acid from the group consisting of aromaticcarboxylic acids of the benzene and naphthalene series and the polyamine is a polyethylene polyamine containing at least 3=nitrogen atoms and 4 to 8' carbon atoms, said diacylated polyamine being dispersed into said water in an amount suflicient substantially to inhibit the tendency of said water to foam on boiling, and boiling said water. I

7. A method of generating-steam from a boiler water having a tendency to foam on boiling which comprises dispersing into said water stearyl betanaphthalene sulfonyl triethylene tetramine in an amount sufiicient substantially to inhibit the tendency of said water to foam on boiling, and boiling said water.

8. A method of generating steam from a boiler water having a tendency to foamon boiling which comprises dispersing into said water stearyl halogenated benzoyl triethylene tetramine in an amount suflicient substantially to inhibit the tendency of said water to foam on boiling, and boiling said water.

9. A method of generating steam from a boiler Water having a tendency to foam on boiling which comprises dispersing into said water a waxlike diacylated polyamine in which the polyamine is a polyethylene polyamine, one of the acyl groups is derived from a fatty acid containing at least 14 carbon atoms, and the other acyl group is derived from the group consisting of aromatic sulfonyl radicals of the benzene and naphthalene series, aromatic-aliphatic acyl radicals in which the aromatic group is from the benzene series and the aliphatic group contains not more than 3 carbon atoms and aromatic carboxyiic acyl groups of the benzene and naphthalene series, said diacylated polyamine being dispersed into said water in an amount sumcient substantially to inhibit the tendency of said water to foam on boiling, and boiling said water.

PAUL G. BIRDQ ARTHUR L. JACOBY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'IENTS Y Number Name Date 2,328,551 Gunderson Sept.- '1, 1943 2,366,727 Gunderson Jan.- 9, 1945 2,442,768 Gunderson June 8, 1948 

9. A METHOD OF GENERATING STEAM FROM A BOILER WATER HAVING A TENDENCY TO FOAM ON BOILING WHICH COMPRISES DISPERSING INTO SAID WATER A WAXLIKE DIACYLATED POLYAMINE IN WHICH THE POLYAMINE IS A POLYETHYLENE POLYAMINE, ONE OF THE ACYL GROUPS IS DERIVED FROM A FATTY ACID CONTAINING AT LEAST 14 CARBON ATOMS, AND THE OTHER ACYL GROUP IS DERIVED FROM THE GROUP CONSISTING OF AROMATIC SULFONYL RADICALS OF THE BENZENE AND NAPHTHALENE SERIES, AROMATIC-ALIPHATIC ACYL RADICALS IN WHICH THE AROMATIC GROUP IS FROM THE BENZENE SERIES AND THE ALIPHATIC GROUP CONTAINS NOT MORE THAN 3 CARBON ATOMS AND AROMATIC ACRBOXYLIC ACYL GROUPS OF THE BENZENE AND NAPHTHALENE SERIES, SAID DIACYLATED POLYAMINE BEING DISPERSED INTO SAID WATER IN AN AMOUNT SUFFICIENT SUBSTANTIALLY TO INHIBIT THE TENDENCY OF SAID WATER TO FOAM ON BOILING, AND BOILING SAID WATER. 